A. M. Glezer

Grain boundary engineering and superstrength of nanocrystals

A new paradigm of hardening of nanocrystals is proposed based on the competing influence of various mechanisms of plastic deformation, i.e., dislocation sliding and grain-boundary slip. It has been confirmed using the results of computer modeling and the experimental data that the use of grain boundary engineering on the basis of the proposed ideas makes it possible to enhance substantially the strength of titaniumbased materials up to ultimate (theoretical) values.

Formation of internal stress fields in rails during long-term operation

The structure and the internal stress fields in R65 rails withdrawn from operation because of side wear after long-term operation are studied and estimated. A high scalar dislocation density (higher by a factor of 1.5–2), the fragmentation of cementite lamellae, and the precipitation of carbide particles are detected in the layers adjacent to the roll surface. The stresses at the boundaries of the particles with the ferrite matrix can exceed the ultimate strength of the steel.

Effect of megaplastic deformation on the magnetic properties of FeNi alloy

The effect megaplastic deformation has on the coercivity and specific saturation magnetization of soft-magnetic equiatomic FeNi alloy is studied at room temperature in a Bridgman chamber by means of X-ray diffraction, Mössbauer spectroscopy and magnetometry. Structural features responsible for changes in the alloy’s properties at different stages of deformation are revealed.

Effect of external actions on the magnetic properties and corrosion resistance of Co 70.5 Fe 0.5 Cr 4 Si 7 B 18 amorphous alloy

Variations in the magnetic characteristics (specific saturation magnetization and coercive force) of Co–Fe–Cr–Si–B amorphous alloy (AA) are studied after high-pressure torsion (HPT) and heat treatment. The behavior of AA magnetic properties is analyzed with respect to structural transformations caused by external actions. The corrosion resistance of AA upon transitioning from an amorphous to a crystalline state is investigated. The established optimum annealing and HPT conditions yield a satisfactory combination of the magnetic properties and corrosion resistance of the investigated alloy.

Features of relaxation processes in FeNi alloy upon megaplastic deformation in a bridgman chamber

Structural and thermodynamic parameters characterizing the process of dynamic relaxation in FeNi alloy are determined by means of XRD structural analysis and instant electromotive force fixation (IEFF) for different modes of megaplastic deformation (MPD) in a Bridgman chamber. The factors that determine the level of dynamic relaxation during MPD are established.

Analysis of structure-phase states in-a-bulk hardened and a head-hardened rails

A layer-by-layer analysis along the central axis and over the fillet of rails for low-temperature service, rails with enhanced wear resistance and contact fatigue resistance, and for senior-grade rails, bulk oil hardened and DT 350 rails head-hardened under different conditions has been carried out by modern material science methods. Quantitative variables have been established and a comparison of structure-phase states, defective substructure and internal stress fields has been made.

Susceptibility of crystalline alloys to deformational amorphization during torsion under quasi-hydrostatic pressure

Features of the transition of Ni50Ti30Hf20, Ti50Ni25, Zr50Ni18Ti17Cu15, and Fe78B8.5Si9P4.5 crystalline alloys with different susceptibilities to amorphization upon annealing and in the amorphous state during intense deformation in a Bridgman chamber are considered. The single- and two-phase crystalline states of the chosen alloys are obtained in different annealing modes. It is shown that the amorphizing rate of crystalline alloys differ substantially at the same degree of deformation; i.e., single-phase crystalline alloys based on titanium nickelide and iron amorphize well, while zirconium-based alloy amorphizes weakly in a manner similar to two-phase iron alloy. We believe that the LDA of crystalline alloys and their corresponding crystalline phases is determined by mechanical, thermodynamic, and concentration factors.

Physical Nature of Structure and Properties Degradation of Rail Surface after Long Term Operation

By methods of optical, scanning and transmission electron diffraction microscopy and microhardness and tribology parameters measurement the changes regularities of structure-phase states, defect substructure of rails surface after the long term operation (passed tonnage of gross weight 500 and 1000 mln. tons) were established. It is shown that the wear rate increases in 3 and 3.4 times after passed tonnage of gross weight 500 and 1000 mln. tons, accordingly, and the friction coefficient decreases in 1.4 and 1.1 times. The cementite plates are destroying absolutely and cementite particles of around form with the sizes 10-50 nm are forming after passed tonnage 500 mln tons. The appearance of dynamical recrystallization initial stages is marked after the passed tonnage 1000 mln tons. It is shown that the operation of steel rails is accompanied by full fractures in surface layers with lamellar pearlite grains and the formation of ferrite–carbide mixtures with nanosized particles. The deformation of steel increases the densities of scalar and excess dislocations, the curvature–torsion values of the crystal lattice, and the amplitudes of internal stress fields. The possible mechanisms of established regularities are discussed. It is noted that two competitive processes can take place during rails long term operation: 1. Process of cutting of cementite particles followed by their carrying out into the volume of ferrite grains or plates (in the structure of pearlite). 2. Process of cutting, the subsequent dissolution of cementite particles, transition of carbon atoms to dislocations (into Cottrell atmospheres), transition of carbon atoms by dislocations into volume of ferrite grains or plates followed by repeat formation of nanosize cementite particles.

Increase in the Saturation Magnetization in a Fe 3 Al Superstructure under Large Plastic Deformations

The effect of large plastic deformations at room temperature in a Bridgman anvil cell on the specific saturation magnetization of the DO3-type ordered (Fe–24 at % Al) alloy has been revealed. It has been found that torsion at high pressure and certain deformation parameters results in the complete suppression of long-range order in the alloy and in the corresponding increase in the specific saturation magnetization by 11% with respect to the equilibrium state. A theoretical model qualitatively describing the revealed phenomenon has been proposed.

Rail Strengthening Nature in the Course of Long-Term Operation

Using the methods of transmission electron diffraction microscopy and measurement of microhardness, the regularities of the change in the structural-phase states and defective substructure of the surface layers of rails up to 10 mm by fillet after long-term operation (the passed tonnage of 1000 million tons gross) are established. The possible causes of the observed regularities are discussed. A quantitative analysis of the mechanisms of strengthening of rails at different distance from the rolling surface by fillet after long-term operation is carried out. It is shown that strengthening is multifactorial in nature and is due to substructural strengthening caused by the formation of nanoscale fragments; dispersion strengthening by carbide phase particles; strengthening caused by the formation of Cottrell and Suzuki atmospheres on dislocations; internal stress fields, formed inside; and interphase boundaries.